Cosmological lithium problem: Difference between revisions

Revision as of 22:48, 18 July 2019

Revision as of 11:19, 28 September 2019

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[[Image:SolarSystemAbundances.svg|thumb|center|800px|Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, residuals within the paradigm of the Big Bang.<ref>{{cite book |last1=Stiavelli |first1=Massimo |year=2009 |title=From First Light to Reionization the End of the Dark Ages |url=https://books.google.com/books?id=iCLNBElRTS4C&pg=PA8 |page=8 |publisher=[[Wiley-VCH]] |___location=Weinheim, Germany |isbn=9783527627370|bibcode=2009fflr.book.....S }}</ref> Li, Be and B are rare because they are poorly synthesized in the Big Bang and also in stars; the main source of these elements is [[cosmic ray spallation]].]]

Older stars seem to have less lithium than they should, and some younger stars have much more.<ref name="MWoo"/> The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed,<ref name=cld>{{Cite news |url=http://www.universetoday.com/476/why-old-stars-seem-to-lack-lithium/ |title=Why Old Stars Seem to Lack Lithium |date=16 August 2006 |author=Cain, Fraser |deadurlurl-status=nolive |archiveurl=https://web.archive.org/web/20160604044857/http://www.universetoday.com/476/why-old-stars-seem-to-lack-lithium/ |archivedate=4 June 2016 |df=dmy-all }}</ref> while lithium is produced in younger stars. Though it [[lithium burning|transmutes]] into two atoms of [[helium]] due to collision with a [[proton]] at temperatures above 2.4 million degrees Celsius (most stars easily attain this temperature in their interiors), lithium is more abundant than current computations would predict in later-generation stars.<ref name=emsley/><ref name="Cain">{{cite web|url=http://www.universetoday.com/24593/brown-dwarf/|archiveurl=https://web.archive.org/web/20110225032434/http://www.universetoday.com/24593/brown-dwarf/|archivedate=25 February 2011|title=Brown Dwarf |accessdate=17 November 2009 |last=Cain |first=Fraser |publisher=Universe Today}}</ref>

[[File:Nova Centauri 2013 ESO.jpg|thumb|[[Nova Centauri 2013]] is the first in which evidence of lithium has been found.<ref>{{cite web|title=First Detection of Lithium from an Exploding Star|url=http://www.eso.org/public/news/eso1531/|accessdate=29 July 2015|deadurlurl-status=yesdead|archiveurl=https://web.archive.org/web/20150801001700/http://www.eso.org/public/news/eso1531/|archivedate=1 August 2015|df=dmy-all}}</ref>]]

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Lithium is also found in [[brown dwarf]] substellar objects and certain anomalous orange stars. Because lithium is present in cooler, less-massive brown dwarfs, but is destroyed in hotter [[red dwarf]] stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun.<ref name=emsley/><ref name="Cain"/><ref>{{cite web|url=http://www-int.stsci.edu/~inr/ldwarf3.html |archive-url=https://archive.is/20130521055905/http://www-int.stsci.edu/~inr/ldwarf3.html |dead-url-status=yesdead |archive-date=21 May 2013 |title=L Dwarf Classification|accessdate=6 March 2013 | first =Neill | last = Reid | date = 10 March 2002}}</ref>

===Less lithium in stars with planets===

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==Proposed solutions==

Numerous studies have been conducted in search of an explanation for this deficiency of lithium, all inconclusive.<ref name=coc>{{cite journal |last=Coc |first=A. |last2=Uzan |first2=J.-P. |last3=Vangioni |first3=E. |title=Standard big bang nucleosynthesis and primordial CNO abundances after Planck |date=2014 |journal=Journal of Cosmology and Astroparticle Physics |volume=2014 |doi=10.1088/1475-7516/2014/10/050 |arxiv=1403.6694}}</ref> One theory suggests that the lithium problem may be partially caused by faster destruction than synthesis of ⁷Li and its progenitor [[beryllium-7|⁷Be]] in [[nuclear reaction]]s, though no conclusive results on the reaction flow in Big Bang nucleosynthesis have been obtained. Newer theories involving physics beyond the [[standard model]], involving not well understood [[dark matter]], have also been proposed to explain the possible destruction of lithium, also inconclusively.<ref name=Bertulani>{{cite journal |last=Bertulani |first=C.A. |last2=Shubhchintak |last3=Mukhamedzhanov |first3=A.M. |title=Cosmological lithium problems |date=2018 |journal=EPJ Web of Conferences |volume=184 |pages=01002 |doi=10.1051/epjconf/201818401002 |arxiv=1802.03469|bibcode=2018EPJWC.18401002B }}</ref><ref name=MWoo>{{cite web |url=http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |title=The Cosmic Explosions That Made the Universe |last=Woo |first=Marcus |date=21 Feb 2017 |website=earth |publisher=BBC |access-date=21 Feb 2017 |quote=A mysterious cosmic factory is producing lithium. Scientists are now getting closer at finding out where it comes from |deadurlurl-status=nolive |archiveurl=https://web.archive.org/web/20170221214442/http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |archivedate=21 February 2017 |df=dmy-all }}</ref> However, one new theory posits that strangeon dark matter (a hypothetical mix of [[strange matter|strange]] and dark matter) may be responsible for the destruction of ⁷Be before it decays to ⁷Li, as the low nuclear binding energy of ⁷Be renders it susceptible to destruction upon collision with strangeons.<ref name=Xu19>{{cite arxiv |last=Xu |first=R. |title=Trinity of strangeon matter |date=2019 |arxiv=1904.11153}}</ref>

==See also==